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Transcript
Pacemakers and Implantable Defibrillator
CARDIAC PACEMAKER










Introduction
Definition
Types
Indication
Pacing modes
Pacingg modalities
Settings
Malfunction and troubleshooting
ICD
Patient’s Management
GOALS







Identify the pacemakers types and indication .
Identify the pacemakers modes and modalities.
How to assess the output and sensitivity .
Basic temporary pacemaker concept .
Wh to d
What
do in
i malfunction
lf
i and
d troubleshoot
bl h
.
To know about the implanted defibrillators .
To know the nursing care post procedure.
INTRODUCTION
y
p
Ap
pacemaker system
is a device capable
of
generating artificial pacing impulses and
delivering them to the heart.
 It consists
i t off a pulse
l ggenerator
t and
d
appropriate electrodes.
 In the past few years electronic pacemaker
systems have become extremely important in
savingg and sustainingg the lives of cardiac
patients whose normal pacing function of the
heart have been impaired

WHAT IS THE PACEMAKER?

Electronic device that provides electrical
stimuli to the heart muscle .
WHAT IS THE INDICATION FOR EACH TYPE ?






TPM:
Post surgical patient ( open heart surgery )
Heart block post myocardial infarction
Symptomatically Bradycardic
Patient who require overdrive dysrrythmia control
Patient whose native rate may be depressed by
medication




i.
ii.
iii.
i
iv.
v.
vi.
PPM:
Symptomatic sinus bradycardiac or atroventricular AV
block
Sinus bradycardia as a result of necessary drug therapy
Advanced AV block with:
asystole >3 sec
escape rate < 40 bpm
catheter ablation of AV node
neuromuscular disease
postoperative AV block that is not expected to recover
Recurrent syncope
y
p attack due to heart disease
PACEMAKER MODES

y
)p
Fixed-rate ((asynchronous)
pacingg


Demand (synchronous) pacing



Delivers pacing stimulus at a fixed rate regardless of
spontaneous cardiac depolarization (nonsensing)
Delivers pacing stimulus when the heart’s intrinsic pacing
fails below a predetermined rate.
Pacing is either inhibited or triggered by the sensing of
intrinsic beats
Atrioventricular (AV sequential) pacing

Delivers pacing stimulus to atrium and ventricle in
physiological sequence with sufficient AV delay.
PACING MODALITIES:

VVI:
( v ) the paced chamber is the ventricle
( v ) the sensed chamber is the ventricle
( I ) the pacemaker response is inhibited
the inhibited response means that the pacer will be inhibited from
pacing if the ventricle is depolarizing unaided

AAI:
( A ) the paced chamber is the atrium
( A ) the sensed chamber is the atrium
( I ) the pacemaker response is inhibited
if the pace maker sensed native P wave it is inhibited from pacing

DDD:
the Ds stand for “dual”either
dual either the atrium or the
ventricle or both may be paced ; either native P
wave or native R wave may be sensed ,and
and the
pacemaker may be inhibited or triggered to
pace , depending on the combination of events
it detects

o
AOO , VOO, DOO :
the first letters of these modes indicate the place of
pacing A=atrium=ventricle, A=dual
in OO modes the pace maker does not detect native
events ( as indicated by O in second position ) and because the
pacer not sensing , it naturally can have no response to
sensed events ( as indicated by the O in the third position )
MODE SWITCH :
It is the pacer detection protocol that allow automatic switchingg of
pacing modes to prevent rapid ventricular pacing in response to rapid
atrial rates

AOO

VOO

DOO
Pacemakers codes
1st letter
Champer(s) paced
A= atrium
V= ventricle
D= dual
2nd letter
Champer(s) sensed
A = atrium
V = ventricle
D = dual
O = none
3rd letter
respond to sensing
I=inhibit (demand)
T= triggered
D= dual
O= none (asynch)
Chamber paced
Chamber sensed
Action or response to a sensed
event
V
V I
APPLICATION OF MAGNET TO A
PACEMAKER TURNS OFF THE
SENSING MODALITY MAKING
THE PACMAKER
ASYNCHRONOUS
WHAT IS THE PACING OR CAPTURE THRESHOLD
( output ) ?
Is the smallest amount of energy from the pacemaker
that consistently provokes contraction of the target
chamber the energy output measured in milliamperes
( mA ) .
HOW IS THE CAPTURE THRESHOLD ASSESSED ?
1-gradually slow the pacing rate , observing carefully for patient tolerance, until
the patient is in his own native rhythm.
2- Set the output to a low value (1 mA) then rise the pacing rate to a level
slightly higher than the patient own rate .
3-if you see only pacing artifacts ( spikes )with no corresponding depolarization
at the same rate or with only intermittent response of the heart ,you have
not yet reached the capture threshold , increase the output by another mA
and test again .
4-repeat until every spike is followed immediately by depolarization of the
target chamber ,then dial in at least twice as much output for the chamber
you are evaluating ,
5-document the threshold ,
WHAT IS THE SENSING THRESHOLD ?
Is the ability of the pacer to detect native cardiac signals P
and R waves , the sensing threshold measured in millivolts
( mV ).
)
HOW IS THE SENSING THRESHOLD ASSESSED ?
1.
2.
3.
4.
5.
Reduce the pacing rate until the patient underlying rhythm is fully emerged
Make the pacer as insensitive to the ventricle as you can by setting ventricular
sensitivity to the higher value
Set the pacing rate a bit higher than the patient rate
Continue decreasing the sensitivity value until at least no more pacing occurs ,
at this point the pacer is sensitive to detect cardiac signals
Document the sensitivity threshold and set the sensitivity at least twice as high
by decreasing the value to half its numeric size, example if the ventricular
sensing threshold is 6mV you may choose a final setting of
3 mV for the ventricle .

Rate
i.
1.
Fixed: stimulus provided at a preset rate (grater
than patient’s
patient s rate)
Demand: stimulus provided when the patient’s
heart falls below a p
predetermined rate (p
(proper
p
sensing is required)
MALFUNCTION AND TROUBLESHOOTING
Failure to Capture
 Failure to Fire (Failure to pace)
 Undersensing
U d
i g
 Oversensing

FAILURE TO FIRE

Spikes are not noted during period of asystole or bradycardia
Causes
i.
ii.
iii.
iv.

Loose connection son the system
Failure of battery or pulse generator
Broken lead wires
Lead wire dislodgment
Interventions
i.
ii.
iii.
iv.
Assure pacing connections
Replace battery or generator as appropriate
Reposition leading wire
ire
Attempt pacing with another pacing system
FAILURE TO FIRE
FAILURE TO CAPTURE

Spike is not followed by a P or QRS complex as appropriate
Causes
i.
ii.
iii.
iv.
v
v.

Loose connections on the system
Failure of battery or pulse generator
Broken lead wires
Lead wire dislodgment or fibrous at site of electrodes
low pacing threshold (output)
Interventions
i.
ii.
iii.
Assure pacing connections
Check threshold and increase o
output
tp t mAm
Repositioning the patient may also resolve the problem
FAILURE TO CAPTURE
UNDERSENSING





p
Inabilityy of the p
pacemaker to sense spontaneous
myocardial depolarization
Pacemaker looses its ability for self-inhibition
Competition between the paced complexes and
intrinsic heart’s rhythm occur
Demonstrated on the ECG by a pacing spike
occurring after or unrelated to intrinsic QRSs
It is a serious malfunction that could lead to
dangerous ventricular dysrhythmia as VT & VF
UNDERSENSING

Causes
i.
ii.
iii.

Inadequate QRS signal (QRS signal not detected
by pacemaker, low sensitivity)
Myocardial ischemia, fibrosis, electrolytes
disturbances
Inappropriate mode selection (asynchronous)
Intervention
o
Increase sensitivity (moving the sensitivity dial
toward its lowest setting)
UNDERSENSING
Undersensing. This transcutaneous temporary pacemaker set in the ventricular
d
demand
d mode
d fi
fires and
d paces appropriately
i t l iin th
the beginning
b i i off the
th strip.
t i The
Th 9th
complex is the patient’s inherent QRS complex which should have been sensed by
the pacemaker. Instead the pacemaker fired.
OVERSENSING




Inappropriate sensing of patients QRS
The pacemaker thinks it detects a QRS complex so it inhibit
itself and does not fire
Result in unexplained pauses in the ECG traces
Causes
i.
ii.

Tall P or T waves
Electrical signals produced by skeletal muscle contractions (during
shivering
hi i or seizures)
i
)
Intervention
i.
ii.
Decrease sensitivity (moving the sensitivity dial toward its highest
setting 20 mV)
setting,
Try to eliminate possible sources of electromagnetic interference in
the patient’s environment
OVERSENSING
What are implantable cardiac defibrillators?
WHAT ARE IMPLANTABLE CARDIAC
DEFIBRILLATORS?
An implantable cardiac defibrillator (ICD) is a small
electronic device installed inside the chest to
prevent sudden death from cardiac arrest due to
life threatening abnormally fast heart rhythms
(tachycardias). The ICD is capable of monitoring
the heart rhythm. When the heart is beating
normally the device remains inactive.
normally,
inactive If the heart
develops a life-threatening tachycardia, the ICD
delivers an electrical "shock(s)" to the heart to
terminate the abnormal rhythm and return the
heart rhythm to normal
IMPLANTABLE CARDIOVERTER DEFIBRILLATOR
INDICATION FOR ICD:
ICD
Patients at risk of developing sudden cardiac arrests due to
ventricular tachycardias and fibrillations are candidates for
ICDs. ICDs do not prevent the occurrence of life-threatening
rhythms,
h th
b
butt can quickly
i kl tterminate
i t them
th
when
h they
th occur.
Recent clinical trials have identified several groups of
patients who should receive ICDs. They are:
•
•
•
•
VT\VF arrest not due to reversible causes.
Spontaneous
p
VT whit structural heart disease
Syncope of unknown etiology with relevant VT\VF
VT in asymptomatic patient with nonsustained VT ,CAD,LVF that
is not suppressible by antiarrhythmic drugs
A MAGNET APPLIED OVER THE ICD TURN OFF
DETECTION ,,AND
AND THEREFOR WITHOUT
DETECTION OF ARRHYTHMIAS NO THERAPIES
CAN BE DELIVERED ,BUT A MAGNET OVER THE
ICD DOES NOT TURN THE PACEMAKER
FUNCTION OF THE ICD INTO ASYNCHRONOUS
PACING MODE
INSERTION OF PACEMAKER

EQUIPPMAENT REQUIRED
one sterile insertion kit which includes:
one gauge angiographic needle
one vessel dilator
g id wires
guide
i
one introducer sheath with homeostasis valve
one introducer dilator
pressure tubing
one basin filled with sterile saline
local anesthetic with syringe and needle
one sterile scalpel and blade
sterile 20 cc syringe
sterile
t il llongg d
drape and
d sterile
t il gloves
gl
WHENEVER POSSIBLE USE FLUROSCOPY
DURING THE WIRE INSERTION ,IF NOT
AVAILABLE URGENT CXR SHOULD BE DONE
TO DETERMAINE THE WIRE PLACEMENT
NURSING CARE POST PACEMAKER INSERTION





ECG monitoringg
Hemodynamic monitoring
Frequent assessment of pacemaker
Electrical safety
Pacing insertion site care
o


Cleaning, dressing, signs of infection
Protect pacemaker from accidental adjustment
Patient & family education
ANY QUESTION ?
REFERENCES
- Critical Care Secrets
Hilda M.Schell / Kathleen A.Puntillo2001
315-326
326 ( 2009 )
- Clinical Cardiology 23, 315
-
MKSAP14 ,American College Of Physicians 2009
- Making Sense Of the ECG
Andrew R Houghton / David Gray 2008